Electromagnetic switches and relays known in the art typically consist of a multi-turn coil wound on an iron core forming an electromagnet. The coil electromagnet is energized by passing current through the multi-turn coil to magnetize the core. The magnetized coil attracts an armature to a first position, which is pivoted to connect or disconnect one or more sets of contacts. When no current is passed through the coil or the polarization of the current is reversed, the coil is moved to a second position in which the contacts are disconnected or connected respectively.
While these switching devices operate satisfactorily in normal applications, it has been found that under extremely high current conditions, e.g. short-circuit conditions, a repulsion force is generated which tends to part the pairs of contacts, which may cause serious damage to the switching device.
U.S. Pat. No. 5,694,099 discloses a switching device which can operate under high current conditions. The switching device has a solenoid actuator with a plunger and a pivot arm. The pivot arm has one end coupled to an outer end of the plunger and the other end bridging and engaging a moving switch blade of the switching assembly. Within the bridging member of the pivot arm, a compression spring is seated to engage the moving blade and provide a further positive pressure to hold the moving contact in engagement with the fixed contact when the pivot arm is in the position to cause the fixed and moving contacts to engage. When the switch is in the “made” condition, the flow of the same current in opposite directions in the parallel paths, which respectively comprise the inlet bus-bar and the moving switch blade, generates an electrodynamic force between them, tending to move the switch blade away from the fixed inlet bus-bar thereby increasing the force applied to the moving contact, and thus resisting any tendency of the contacts to separate under conditions of high current.
High current switch devices, such as those described above, provide adequate switching. However, these devices, and in particular the pivoting arms, tend to be relatively complicated, which increases the cost and increases the overall size of the switching device. It would, therefore, be beneficial to provide a switching device which could be used in high current environments, but which wall easy and inexpensive to manufacture and which could operate effectively in a reduced space.